internal revenue code; conformity; deductions.

HB 2153 updates Arizona's tax code to align with specific versions of the federal Internal Revenue Code (IRC) for different tax years. It defines "internal revenue code" for Arizona income tax calculations as the federal IRC as it existed on fixed dates (e.g., January 1, 2024 for 2023-2024 tax years), including retroactive federal provisions enacted during those years but excluding changes after the reference date. This affects Arizona taxpayers and businesses filing state returns by determining which federal tax rules Arizona applies. The bill does not change tax rates or create new deductions but standardizes the reference point for state tax computations. It is a technical conformity measure, not a policy change.